Topographical and Geological Study on submarine canyons off the Pacific Coast in the Japanese Islands

日本岛屿周围的海底峡谷分为66个海底峡谷系统。我从地形和地质的角度研究了分布在日本太平洋沿岸的21个系统。日本东北部的海底峡谷似乎主要是海底重力流（如水下碎屑流、浊流等）对海底侵蚀的结果。日本西南部和北海道附近的海底峡谷是类似的峡谷。根据断层偏移、褶皱轴走向和其他地质构造的不同，他们的平面观点在体系形态和峡谷轴走向上有所不同。各地区峡谷的平面形态和形成机制存在一定的差异，但沿峡谷轴线的纵向地形剖面显示出所有峡谷的共同特征。以两个缓坡（坡度A1: 0.005-0.006，坡度A2: 0.010-0.018）和两个陡坡（坡度B1: 0.030-0.036，坡度B2: 0.064-0.106）为地形单元的纵剖面。斜坡A1和A2相当于日本东北部的上陆坡和日本西南部的弧前盆地，斜坡B1和B2相当于日本东北部的下陆坡和日本西南部的大陆斜坡。所有实际的纵剖面都可以在这些地形单元的组合中得到近似。另外，还发现了咸野misaki深海扇，绘制了bosu - sagami峡谷系统的峡谷系统详细图。

Submarine canyons around the Japanese islands are divided into 66 submarine canyon systems. I have studied twentyone systems of them which distributed off the Pacific coast of Japan from the topographycal and geological view points. The submarine canyons off NE Japan appears to be chiefly the result of subbottom erosion by some submarine gravity flows.e.g.subaqueous debris flows, turbidity currents and others. The submarine canyons off SW Japan and Hokkaido are resequent canyons. Their plan views vary in sytem patte and trend of canyon axis depending on the offset of faults, trend of fold axis and the other geological structures. There are some differences in plan view and formational mechanism of canyons among those regions, however, the longitudinal topographic sections along canyon axis show a charactcteristic common to all the canyons. Those londitudinal sections divided into two gentle slopes (slope A1 : 0.005-0.006, slope A2 : 0.010-0.018) and two steep slopes (slope B1 : 0.030-0.036, slope B2 : 0.064-0.106) as topographic units. The slope A1 and A2 are equivalent to the upper continental slope off NE Japan and the forearc basins in SW Japan, the slope B1 and B2 are equivalent to the lower continental slope off NE Japan and the continental slopes of SW Japan. All the actual longitudinal sections can be approximated in assemblage of these topographic units. The other results are the discovery of the Shio-no-misaki deep sea fan and a drawing up the detailed chart of canyon systems in the Boso-Sagami canyon systems.